Malignant Hyperthermia

A listener to the show from Australia, Jerry Barrett, sent me this article he had written on an ambulance transport patient and the information he discovered following that call.  It’s a great look at Malignant Hyperthermia for the readers here.  The text below is reproduced with permission from the author.

References and links are available at the end of the article

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Malignant Hyperthermia: An on road experience by Jerry Barrett

‘Malignant Hyperthermia [MH] is an inherited myopathic disorder characterized by a marked increase in metabolic rate. The reported incidence varies considerably but is approximately 1:50,000, rapid and effective treatment is essential to avoid mortality: over the last 30 years the fatality rate has fallen from 70% to about 5%.” 1

This paper describes a recent experience with a collapsed patient suffering from MH and the clinical implications of this syndrome to pre-hospital care practitioners.

The Case

We received a Priority One call for an unresponsive male occupant of a motor vehicle, collapsed at the steering wheel in a shopping centre car park.

On arrival, the initial visual assessment presented a middle aged male in the driving seat slumped forward over a car’s steering wheel. Initial verbal prompts failed to illicit a response; the patient had a GCS of 10/15 [E1,V4,M5]. There was no obvious indication of alcohol, CO, or substance abuse however the patient appeared to have a very wet shirt and his skin was hot to touch. A patent airway was evident from incoherent mumblings that could be heard once I approached the patient. A bystander who had commenced initial care of the patient commented that the patient seemed to respond well to cold water being thrown over him [also explaining the wet appearance of the patient]. 1

Following the initial primary survey indicating GCS 10/15, SPO2 99%, pulse 99 bpm, NIBP 170/70 and resps 24, the patient seemed to gain some composure and sat back in his seat. Although not aware of his surroundings the patient volunteered the fact that he suffered from Malignant Hyperthermia and that he had started to feel hot and dizzy in the shopping centre so returned to his vehicle in an effort to drive home.

As there was no thermometer available, I had no indication of the actual temperature of this patient and although there was an apparent rise in the GCS to 12/15 [3,4,5] I indicated to my partner that time was of the essence and that we had to extract the patient from the car as soon as possible.

Once extracted from the vehicle and secured on the stretcher I commenced treatment. St John Ambulance Western Australia guidelines for hyperthermia tend to concentrate on heat stoke/ hyperglycaemia as the cause and indicate ‘time critical’ and the need for active cooling and IV resuscitation. As I was unable to determine an exact temperature of the patient I feared the worst and inserted a 14G IV cannula prior to urgent transport to the nearest appropriate hospital, less than10 minutes away. One hundred per cent oxygen via a re-breather and 3 lead ECG was applied [confirming tachycardia], and one litre of isothermic normal saline was commenced STAT, a phone call was made to the hospital ED to pre-warn them of our impending arrival.

En route we began active cooling of the patient by using cold packs under the axilla and groin as well as a wet burn dressing to the head and air conditioning redirected onto the patient. This initial ‘cool down’ made a significant improvement to the patient’s condition and his GCS rose to 15/15. Once the patient had regained his composure he confided that he had been experiencing headaches and episodes of feeling hot and dizzy in the weeks prior to this event but did not wish to go to hospital.

Although he had been told that he had MH, and was aware that it was potentially fatal he refused to buy a Medical Alert bracelet for the reason that it might put up the price of his medical insurance! It was explained to him the implications of not having any indication of his condition should he have another episode and not be able to convey his condition verbally to emergency medical services.

Malignant Hyperthermia

“Malignant Hyperthermia [MH] is a rare pharmacogenetic disorder” however it does exist in the general population and can possibly be induced by stress or the use of Methylenedioxymethamphetamine [Ecstacy] as well as the common trigger agents such as Scoline and Halothane. In Western Australia Methoxyflurane is still in current use with St John Ambulance as an analgesic agent and its close relationship to Halothane makes it a possible trigger agent for MH, and in WA is therefore contraindicated in susceptible patients. 2, 3, 4

“There are unquantifiable rare things in life such as ‘hens teeth’, rocking horse poo and honest politicians and quantifiable rare things such as winning the Oz Lotto 1:8,000,000 or risk of death by lightning strike 1:1,000,000 or coming across MH 1:50,000.” 2

There is no clinical sign or cluster of signs to indicate MH, MH is a clinical chameleon. All signs of MH are non specific and may arise from multiple causes. Exposure to known triggering agents without reaction does not exclude MH susceptibility and there are many possible differential diagnoses for the various signs and symptoms: such as Sepsis, Hyperglyceamia or Substance [Ecstasy/ Amphetamine] abuse. 2

Etiology of Malignant Hyperthermia

MH is an inherited disorder. The genetics of MH are complex. Mutations in the human ryanodine receptor in skeletal muscle [a calcium release channel with a role in excitation-contraction coupling] are apparent in some families. Predisposition to MH has been defined in only three rare clinical myopathies. Inheritance of the MH gene and contact with specific agents can trigger abnormal calcium release from the sarcoplasmic reticulaum into the cytoplasm. This leads to myofibrillar contraction, depletion of high energy muscle phospate stores, accelerated metabolic rate, increased carbon dioxide and heat production, increased oxygen consumption and metabolic acidocis. The usual triggering agents are succinylcholine or any volatile anaesthetic agents. 3

Clinical Indicators of Malignant Hyperthermia

As previously noted, MH presents as a clinical chameleon1 even in the clinical setting. Therefore the ability to recognise this condition in the pre-hospital phase of assessment or treatment can be very difficult.

Below is a list of classic signs/ symptoms associated with a patient suffering from MH:

• Muscular Rigidity
• Tachycardia
• Tachypnoea [increased CO2 excretion]
• Increased Oxygen consumption
• Metabolic Acidosis
• Hyperthermia

A visual alert that the patient suffers from this rare condition would be of great advantage when trying to resuscitate a tachycardic, pyrexic patient with possible tachypnoea of unknown cause This will not always be the case, even in the clinical setting and one may need to rely on verbal indication of such conditions being suspected. These symptoms plague us every weekend on the streets with Ecstasy overdoses.

Management of Malignant Hyperthermia

MH is a clinical emergency and in the pre-hospital environment is an acute situation due to the rapid progression of this condition and the high mortality factor associated with it.

A suggested guideline for treating patients suffering from MH might include:

Administer 100% Oxygen

Gain IV access with large bore IV [possibly prior to the active cooling stage in order to maintain optimal conditions for IV access].

ECG monitoring

Active Cooling: chemical ice packs to axilla and groin regions, vehicle air conditioning flow directed onto patient and latent evaporation to head using damp swap/ dressing. And if available isothermic or cool IV fluid.

Urgent transport to an appropriate medical facility. This should also include a call to the ED to advise them of the condition of the patient and give the medical staff time to prepare for their arrival.

Summary

Malignant Hyperthermia is a rare but deadly condition. The rapid administration of Dantrolene Sodium is an effective treatment of MH once it has started its acute cycle; the drop of mortality from 80% to approximately 5% now gives us hope that rapid diagnosis and intervention reduces mortality. The price, short shelf life and rare use of Dantrolene make its supply limited, and there appears to be no national guidelines determining what supply level is mandatory in critical care environments.

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Jerry has been a Paramedic since the early 80’s and served in several Middle Eastern Armed Forces after leaving the British Armed Forces. Moving to Perth in 2003 with his family he initially worked in the Operating Theatres as a Senior Anaesthetic Technician before joining St John Ambulance in 2004. Also gaining a qualification in Traditional Chinese Medicine Jerry also operates a First Aid Training company and has always been passionate about teaching. Jerry operates out of Cockburn Station in the Southern suburbs of Perth.

References

1. Textbook of Anaesthesia: 4th edition. Alan Aitkenhead, David Rowbotham & Graham Smith. Churchill Livingstone.

2. Malignant Hyperthermia MS PowerPoint presentation, Dr Mark Waddington, RPH March 2005.

3. Induction of Malignant Hyperthermia in Susceptible Swine by Ecstasy by Fiege M, Wappler F, Weisshorn R, Gerbershagen MU, Menge M, Schulte Am Esch J. Assistant Professor of Anaesthesiology, dagger Professor on Anaesthesiology, Staff Anaesthesiologist, Research Fellow, Professor of Anaesthesiology and Chair, Department of Anaesthesiology, University Hospital Hamburg-Eppendorf. Anaesthesiology. 2003 Nov;99 [5]:0032-1136

4. Stress-induced Malignant Hyperthermia in a head injured patient. Case report. Feuerman T, Gade GF, Reynolds R. Division of Neurosurgery, University of California, School of Medicine, Los Angeles.

Other Links:

Malignant Hyperthermia Association of the United States

WebMD on Malignant Hyperthermia